Abstract

A pressure gauge is described in which the displacement of a pressure diaphragm is measured by recording photographically the motion of interference fringes formed by light reflected from the diaphragm and from an adjacent stationary mirror. The instrument is simple and unusually accurate and stable. Typical observed performance: frequency range, zero to over ten thousand c.p.s.; pressure range, zero to five thousand p.s.i.; absolute error, less than one‐half percent. Calibration is carried out under static conditions and the response is linear. Presentation of the data is direct and the analysis of the records simple. Other broad fields of application of the new recording principle are indicated.